This invention relates to an apparatus for acquiring information from sensor measurements made on a body moving with respect to a stationary observer. More particularly, this invention relates to transmission means for acquiring temperature, pressure, torque, strain and the like sensor measurement data from a rotating object or device.
Since various rotating machines such as turbines, motors and generators may often be operated under critically optimal or stressful conditions, the need for accurately determining internal device conditions has increased. This greater need for sensor data generally occurs because of two reasons. First, it is becoming increasingly desirable to operate various machines at optimal or near optimal conditions and doing so requires greater information on various parameters associated with the rotating parts themselves. In these situations indirect or secondary data measurements from peripheral sensors may not be sufficiently accurate, reliable or reflective of actual internal conditions. Second, as various rotating devices are operated at increasingly higher load ratings, it becomes increasingly desirable to accurately determine system conditions which should not be exceeded. Accurately sensing these conditions is important to ensure that protective control systems operate in a sufficiently adequate manner, such as by reducing or cutting off the power to the system prior to device damage. Furthermore, the emergence of digital and analog control systems which are implemented on large-scale integrated circuit chips has greatly facilitated the ability to implement control systems having a large number of input signal parameters.
In the past, sensor information transmission between rotating and fixed parts has been difficult and costly for several reasons. For example, a method of providing electrical power for the rotating sensors and transmission system must be provided. Battery power is inconvenient for such systems because of the relatively short lives of chemical batteries. Accordingly, other information and transmission systems have employed direct slip ring connections between the stationary and rotating parts. However, this is an inconvenient power transmission method which often obscures the signal with noise. Furthermore, slip ring connections are difficult to maintain, require regular attention and generally involve some degree of mechanical interference. Because of the problems associated with the brush connections for providing power to various rotating electronic data generating systems, others have employed reactive coupling to transfer the desired power. For example, transmission of desired power may be affected by radio frequency electromagnetic coupling between a fixed coil and a coil rotating with the motor or generator shaft. However, because large motors and generators in particular often produce relatively high levels of radiated electromagnetic noise, conventional data acquisition systems may experience severe noise problems. Additionally, it is not only necessary to provide power to a rotating data acquisition system, it is also necessary, in conventional systems, to provide a second independent channel for the transmission of data signals from the rotating body to a relatively fixed observer. This is accomplished in conventional systems by the transmission of frequency or amplitude modulated carrier signals. Moreover, these systems are also subject to noise problems and are unnecessarily complex and costly.